Telephone-exchange system



Nov. 8, 1927.

E. E. HINRICHSEN TELEPHONE EXCHANGE SYSTEM Sheets-Sheet 1 Filed March 51. 1926 Wye/7mm 1 Edward /7//7//6/75/7.

h g MM Nov. 8, 1927.

E. EfHlNRICHSEN TELEPHONl-J EXCHANGE SYSTEM 4 Sheets-Sheet 2 Filed March 51, 1926 mam wk Nov.8, 1927. 1,648,122

E. E. HlNRlcHsEN TELEPHONE EXCHANGE SYSTEM iled March 31. 1926 4 Sheets-Sheet 3 Nov. 8, 1927f 1,648,122

E. E. HINRICHSEN TELEPHONE EXCHANGE SYSTEM W Filed March 51. 1926 4 Sheets-Sheet 4 first idle trunk in the group is marked.

Patented Nov. 8, 1927.

UNITED STATES PATENT OFFICE.

EDWARD E. I-IINRIOI-IfiiEN, OF NEW YORK, N. Y., ASSIGNOR TO BELL TELEPHONE LAB- ORATORIES, INCORPORATED, OF NEW YORK, N. Y., A COBPQRATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed March 81, 1926. Serial No. 98,654.

The invention relates to telephone exchange systems and more particularly to systems of the class wherein automatic switching apparatus is employed either entirely or in part for the establishment of conversational connections.

In telephone systems employing switches of the coordinate type, connections are established to a switch, the desired line or group of trunks is then marked and the links of the switch tested to selectan idle one for completing the connection. If no idle links are available, the connection may fail. In establishing. a connection to a pri vate branch exchange in such a system, thre at is therefore possible that, although a plurality of trunks may be idle, if the first one tested is reached through av group of links all of which are busy, the connection may not be completed.

It is an object of the present invention .to increase the availability of trunk groups.

A feature of the invention lies in means for testing the trunks of a group comprising means operated when all the paths leading to a marked idle trunk are busy, to repeat the test.

Another feature of the invention lies in means for rendering busy the trunk to which no paths are available and repeating the test in connection with a second idle trunk.

To this end the test relay of the first idle trunk is locked up and the control of the link testing arrangement transferred to the next idle trunk whereby the group of links serving such idle trunk is tested. This operation may be repeated as long as idle trunks exist. If no corresponding idle links and trunks can be found a busy signal will be returned to the calling subscriber.

The drawing comprises four sheets which when placed in order as shown in Fig. 5 disclose as much of an automatic exchange system as is necessary to give an understanding of the invention. The operating circuits of the switches have been skeletonized where their operation is not essential to an understanding of the invention.

frame connector.

Fig. 1- shows another portion of the incoming marker. This portion includes the controlling equipment for PBX operation.

Fig. 5 illustrates the order in which the sheets ofv the drawing should be arranged. The invention has been embodied as shown inthe above mentioned drawings in a system of the type disclosed and claimed in the United States patent to W. W. Carpenter, No. 1,623,777, granted April 5, 1927 and reference is made to that patent for the details of the operation omitted in the present application.

W hen a call is initiated, the calling subscribers line is extended through a line switch to a sender and to the incoming side of a district selector. The sender is operated in accordance with dial pulses transmitted by the calling subscriber and sets the outgoing marker to control the extension of the call to the incoming selector whereupon the sender sets the incoming sender which in turn sets the incoming marker. This marker now picks one of five final translators such as 300 each serving 2000 lines, associating itself therewith by means of final translator connector310.. The final translator 300 is then positioned. in accordance with the hundreds and tens designationsset up in the incoming marker. With final translator 300 positioned it prepares a test circuit for the vertical magnet 205 or 206 which controls the vertical row including the called subscribers line. Next, the final frame connec tor 320 having access to the final frame in the selected choice is operated. The purpose of this frame connector is to associate the control circuit of the marker with thehori- 100 Zontal operating and testing leads of the final switch and with the incoming selector operating magnets. Relay 321 is the relay individual to frame 200.

PBX trunks may be arranged in groups of varying sizes. W here the group contains more than 10 trunks it is divided into subgroups for the purpose of testing. The testing equipment shown is arranged to test the subgroups of 10, one at a time, in succession until a sub-group is found containing an idle trunk.

Each PBX trunk group is identified at the final frame by a call number corresponding to which a call circuit occupies the position similar to a subscribers line. This identifying call circuit may be located anywhere on the frame in the same vertical rows with direct subscribers lines, if desired. If a PBX trunk group contains an even ten trunks, five of these may occupy a vertical row on one final frame and the other five a vertical row on a second final frame in the same terminal choice. Each trunk will therefore be served by one-fifth of the links in a final frame, or one horizontal group. If the number of trunks in a group is not an even multiple of ten, the full sub-groups of ten are arranged as explained, and the testing equipment is arranged to take into account the location of any odd trunks.

The testing equipment consists of a series of ten testing relays 400, one for each trunk in a full sub-group. Means is provided (not shown) to identify the point at which testing starts, to mark the end of the trunk group and to count the number of subgroups tested.

Assuming that a call is made to a private branch exchange having a group of twenty trunks appearing in the vertical rows 207 and 208 of the final switch 200 and in two similar vertical rows of another final switch in the same final group, the operation proceeds in the manner explained in the above identified Carpenter patent to a point where the final translator 300 is operated. Assuming that the proper relays at the translator 300 are operate 1, a circuit will be closed for relay 420. Relay 420 in operating causes the operation of relays 421 and 422 which serve to alter the testing circuits to conform to the necessities of PBX testing.

With translator 300 operated, a test circuit ,for the first trunk, which is the called line,

may be traced from battery through the low er vinding of relay 401, upper back contact of relay 411. and thence through the winding of relay 331, through the final translator connector 310, through the final translator 300 to the sleeve conductor of the first trunk. conductor 209 of trunk 210.

The test circuit for the second trunk in the group may be traced from battery through the lower winding of relay 402, upper back contact of relay 412, winding of relay 332 through final translator connector 310, final translator 300 to sleeve conductor 211 of trunk 212. Similar test circuits are coInpleted for each trunk of the first sub-group. If all the trunks of this subgroup are busy, relays 401, 402, 406, etc. will be operated. These relays lock through their upper windings and front contacts to the back Contact of relay 425.

The operation of relay 422 as previously described closes a circuit from battery through the winding of relay 423, right back contact of relay 424, front contact of relay 422, the left back contact of relay 425, winding of relay 426 to ground. The operation of relay 423 closes an obvious circuit for relay 427 which relay connects ground to conductor 428. Both relays 423 and 427 are slow to operate and provide a suilicient interval for the testing relays to adjust them selves. When relay 427 operates, relay 425 is operated in acircuit over the front contacts of all the test relays 400, right back contact of relay 429 to grounded conductor 428. Relay 425 opens the locking circuits of the test relays 400 releases relays 423 and 427 and causes the transfer of the test conductors from the final translator 300 to the next sub-group of trunks.

Let us assume that trunk 210 is idle. No ground will appear on the sleeve conductor 209 and relay 401 will not be operated. hen relay 42? operates grounding conductor 428, a circuit will be completed from battery through the winding of relay 411, lower back contact of relay 401, the right back contact of relay 429 to grounded conductor 428. Relay 411 operates and locks over its inner upper front contact to conductor 428. The circuit of relay 425 is not completed and relay 42'? remains operated to hold relay 411 operated. The operation of relay 411 completes a circuit from battery through the winding of the vertical operating magnet 206, through the final trans lator 300, final translator connector 310, outer lower front contact of relay 411, inner left back contact of relay 424 to ground. The operation of relay 411 also completes a circuit from battery on the sleeve conductor 209 through translator 300 and translator connector 310, winding of relay 331. outer upper front contact of relay 411, left back contact of relay 429, winding of relay 430 to ground. Relay 331 operates in this circuit and extends ground over its front contact to the winding of relay 325 which serves to associate the group of relays 350 with the proper links in the final switch 200. An incoming frame connector and a trunk connector (not shown) serve to associate the group of relays with the incoming selector 100 and thetrunk group 220 respectively.

A test is now performed by the testing relays 350 in the marker to determine an idle path through the incoming selector switch 100 over the trunk group 220 and through the final switch 200 to the idle PBX trunk. A three point test is required to select such an available path.

The testing relay set 350 consists of double Wound test relays 361, 362, 363, etc., each serving to test one of the successivetrunks of any group, such as group 220, leading from the incoming frame to the final frame. The relay 361 serves to .test the first trunk in each group such as the trunk 203 in a circuit from battery through the left Winding of relay 361, through certain apparatus (not shown), the test conductor 221 of the trunk 203 to the control circuit 120 of that trunk. Relay 362 tests the next trunk by means of a circuit through the left Winding of relay 362 to test conductor 222 of trunk 204. In like manner, succeeding relays serve to test the successive trunks of the group. If any one of these trunks is busy,ithe correspondingtrunk relay will energize.

The horizontal links of the final switch 200 are tested by means of relays 371, 372, 373, etc., there being as many 01 these relays as there are horizontal links in one of the sections 201 or 202. Relay 371 serves to test the first link in any sect-ion such as the link 214 by means of a circuit from battery through the Winding of said relay over the inner front contact of relay 325, contact of relay 321, left Winding of magnet 213 to the sleeve conductor, of the link 214. In like manner, the other horizontal test relays 372, 373, etc., serve to test the remaining horizontal links in the group 201. The operation of any one of the relays 371, 372, 373, etc., closes an obvious circuit of the corresponding relay 361, 362, 363, etc.

Similar circuits are also provided for testing the horizontal links of the incoming switch. Relay 381 serves to test the firstlink in any section such as link 114 by means of a circuit from battery through the Winding of said relay through apparatus (not shown), left Winding of magnet 102 to the sleeve conductor of the link 114. In like manner relays 382, 383, -etc., serve to test the remaining links in the group 201. The operation of any one of the relays 381, 382, 383, etc. also closes a circuit for operating the corresponding relay 361, 362, 363, etc. Therefore should any one of the elements comprising a switching path of this group be busy, the corresponding test relay will be operated preventing the use of that switching path for completing the connection.

When the incoming selector is ready for use, ground is connected to the armature of relay 363, and a circuit is closed over the back contact of the first unoperated double Woundrelay 361, 362. 363, etc, to operate one of the relays 351, 352,353, etc. Relays 351,

352, 353, etc., test the operating circuits of the incoming horizontal magnets, and initiate the test of the final horizontal magnets. The operation of magnet 206 has already been described. Assuming that the circuits of the horizontal magnet 102 of the incoming selector and of magnet 213 are int-act, these magnets are operated and complete the circuit to the trunk 210.

However, if none of the paths having access to trunk 210 is free, all of the relays 361, 362, 363, etc., are operated. A series circuit will be closed over the front contacts of re lays 363, 362, 361, etc, front contact of relay 421 to the Winding'of relay 429. Relay 429 operates and closes a circuit from grounded conductor 428 over its outer front contact, inner lower front contact of relay 411, upper Winding of relay 401 to battery. Relay 401 locks to the back contact of relay 425 marking the trunk 210 busy to the test circuit. Relay 411 will remain operated under the control of relay 427 but the operation of relay 429 will prevent the operation of any other. of the relays 412,416, etc. at this time The operation of relay 429 opens the circuit of relay 331, which in turn releases relay 326 and disconnects the test relays 350 from the group of switching paths serving trunk 210. Relays 361, 362 and 363 remain locked to the back contact of relay 424. Relay 429 also closes an operating circuit for relay 424 from grounded conductor 428. Relay 424 in operating opens the circuit of relay 423 Whichin turn releases relay 427. Relay 424 also disconnects ground from the Winding of the vertical magnet 206 permitting that magnet to release. In addition it opens the locking circuits Off relays 361, 362 363, etc.

As soon as one of relays 361, 362, 363, etc., releases the operating circuit of relay 429 will be opened to in turn release relay 424. The release of relay 424 permits the reoperation of therelays 423 and 427. Since there were idle PBX trunks in the sub-group, relay 425 Was not operated and relay 401 corresponding to the artificially busy line remains locked. Therefore the reoperation of relay 427, grounding conductor 428, completes a circuit over the back contact of relay 429, front contact of relay 401, back contact of relay 402, winding of relay 412 to battery. Relay 412 looks to conductor 428 and closes a circuit from ground through'the Winding of relay 430, back contact of relay 429. upper front contact of relay 412. Winding of relay 332-through the final translator connector 310 and the final translator 300 to the test conductor 211 of trunk 212 to wh ch battery is connected since the trunk is idle. The vertical magnet 206 will again. be operated over .the lowermost front contact of relay 412. Relay 332 operates in the above traced circuit closingthe circuit of relay 326, to associate the relays 350 with the sub-group of switching paths serving trunk 212. The group of relays 350 will now test the incoming links, the final links and the trunks of this group to determine if a tree path exists therein. It all of the paths to this trunk are also busy, the operation above described will be repeated. If there are no paths available to the last idle trunk of the said group the second sub-group of ten trunks will be tested as described in the above identified Carpenter patent. Only after the switching paths serving the last idle trunk leading to the PBX have in turn been found busy will the line busy signal be given to the calling subscriber.

hat is claimed is:

1. In a telephone system, an incoming trunk, a plurality of outgoing trunks, means tomark an idle outgoing trunk, a plurality of switching paths available to said incoming trunk and having access to said outgoing trunks, means to test those switching paths available for interconnecting said incoming trunk and said marked outgoing trunk, and means effective if none of said available switching paths is idle to repeatthe testin connection with another idle outgoing trunk.

2. In a telephone system, an incoming trunk, a plurality of outgoing trunks, a plurality of switching paths for interconnecting said incoming and outgoing trunks, each outgoing trunk being served by a group of said paths, means to mark an idle outgoing trunk, means to test the group of switching paths serving said outgoing trunk, and means effective if none of said group of switching paths is idle to repeat the test in connection with another idle outgoing trunk.

3. In a telephone systems, an incoming trunk, a plurality of outgoing trunks, means to mark an idle outgoing trunk, a plurality of switching paths, means to select an idle switching path from said incoming trunk to said marked outgoing trunk, means effective it no idle switching path exists to render said marked outgoing trunk busy, to mark another idle outgoing trunk and to select an idle switching path between said incoming trunk and said other outgoing trunk.

4-. In a telephone system, an incoming trunk, a plurality of groups of outgoing trunks. means to select a group of said outgoing trunks containing an idle trunk, means to mark said idle trunk, a plurality of switching paths available to said incoming trunk and having access to said outgoing trunks, means to select an idle one of said switching paths, means effective if no idle switching path exists to said marked outgoing trunk to render said outgoing trunk busy, to mark an idle trunk in another group of outgoing trunks, and means to select an idle switching path in said other group between said incoming trunk and said other idle trunk.

to mark an idle outgoing trunk, a plurality of switching paths available to said incoming trunk and having access to said outgoing trunks, each switching path comprising a plurality of elements, means to test each element of a switching path to select an idle switching path between said incoming trunk and said marked outgoing trunk, and means effective if no idle switching path exists to render said outgoing trunk busy and to cause the marking of another idle trunk and the testing of the elements of another switching path.

6. In a telephone system, an incoming trunk, a plurality of outgoing trunks, means to mark an idle outgoing trunk, a plurality of groups of switching paths available to said incoming trunk, each group having access to one outgoing trunk at a time, means to test all the switching paths in a group having access to said marked outgoing trunk, means effective it no idle switching paths exist in said group to render said marked outgoing trunk busy and to cause the marking of another idle trunk and the testing of the switching paths comprisingthe group having access to said other trunk.

7 In a telephone system, an incoming trunk, a plurality of outgoing trunks, means to mark an idle outgoing trunk, a plurality of groups of switching paths available to said incoming trunk, each group having access to one outgoing trunk at a time and each switching path comprising a plurality of elements, means to simultaneously test each element of the group of switching paths having access to said marked trunk, and means efiective if no idle switching path exists in said group to render said marked outgoing trunk busy and to cause the marking of another idle trunk and the testing of the elements of the group of switching paths having access to said other trunk.

8. In a telephone system, an incoming trunk, a plurality of outgoing trunks, means to mark an idle outgoing trunk, a plurality of groups of switching paths available to said incoming trunk, each group having access to one outgoing trunk at a time, means to test a group of switching paths having access to a marked trunk and means repeatedly eii'ective if no idle switching path exists in such a group to render the marked outgoing trunk busy and to cause the marking of another idle trunk and the testing of the group of switching paths having access to said other trunk.

9. In a telephone system, an incoming trunk, a plurality of outgoing trunks, means to mark an idle outgoing trunk, a plurality of groups of switching paths available to said incoming trunk, each group having access to one outgoing trunk at a time and each switching path comprising a plurality of elements, means to simultaneously test each element of a group of switching paths having access to a marked trunk and means repeatedly'eifective if no idle switching path exists in such a group to render the marked outgoing trunk busy and to cause the marking of another idle trunk and the testing of the elements of the group of switching paths having access tosaid other trunk.

In Witness whereof, I hereunto subscribe my name this 29 day of March, A. D. 1926.

EDWARD E. HINRIGHSEN. 

